1. Technical Field
The present invention relates to a base station test unit for testing a base station in a mobile communications system and, more particularly, to a method and system for measuring the standing wave ratio for a transmission antenna and a reception antenna so as to test a radio unit of the base station.
2. Related Art
In general, a mobile communications system, such as a code division multiple access (hereinafter referred to as "CDMA") system includes a plurality of base stations, a mobile station, and a BSM (base station manager). The base stations thereof are connected via radio with the mobile station so as to enable each of the base stations to communicate with a PSTN (public switched telephone network). In order that the base stations communicate smoothly with the PSTN, there must be a periodic check and diagnosis as to whether or not there is an abnormal state at the base station or the base station is out of order. To meet this requirement, a base station test unit is required to test the base station and the test unit has the function of monitoring and diagnosing for the existence/nonexistence of the base station and any disorder at the base station.
The base station test unit for testing the base station can be used to perform a number of test functions. In particular, if there is damage to a radio unit of the base station having an external antenna, the test unit is useful in testing whether or not there is damage to the antenna or whether or not there is damage to the radio unit of the base station. A characteristic value which is determinative as to the existence/nonexistence of the radio unit of the base station and as to damage to the base station is the voltage standing wave ratio (hereinafter, referred to as "VSWR"). Therefore, the radio unit of the base station can be tested by measuring the VSWR. For reference, the VSWR has a value indicating the size of the standing wave ratio generated by voltage in the transmission path and the ratio is obtained by dividing a maximum value of the standing wave by a minimum value of the standing wave.
Nevertheless, in prior systems, there is a limit to measurement of the VSWR since, in such systems, hardware for measuring the VSWR and a controller capable of controlling the hardware are separately installed. Therefore, there has been a need for the development of a method and system for measuring VSWR without employing any other device for testing the radio unit of the base station in a mobile communications system.
The following patents are considered to be representative of the prior art related to the invention, but are burdened by the disadvantages discussed herein: U.S. Pat. No. 4,380,767 to Goldstein et al. entitled Controlled Antenna Tuner, U.S. Pat. No. 4,479,087 to Althouse entitled Standing Wave Ration And Power Meter, U.S. Pat. No. 4,584,650 to Kozuch entitled Method and Apparatus for Determining and Directly Measuring the Voltage Standing Wave Ratio of an RF Transmission System, U.S. Pat. No. 4,739,515 to Herzog entitled Voltage Standing Wave Ratio Bridge Measuring Circuit, U.S. Pat. No. 4,860,024 to Egashira entitled Antenna for a Portable Radiotelephone, U.S. Pat. No. 4,290,009 to Sanpei et al. entitled Standing Wave Ratio Detecting Apparatus, U.S. Pat. No. 4,262,246 to Fujii entitled Standing Wave Ratio Detecting Apparatus, U.S. Pat. No. 4,249,127 to Morgan entitled Standing Wave Measuring System, U.S. Pat. No. 4,110,685 to Leenerts entitled Standing Wave Ratio Measurement Instrument, U.S. Pat. No. 4,041,395 to Hill entitled Transmitter Performance Monitor And Antenna Matching System, U.S. Pat. No. 4,117,493 to Altmayer entitled Radio Antenna, U.S. Pat. No. 4,422,078 to Cremeen entitled Full Wave Communication Antenna, U.S. Pat. No. 4,096,441 to Schwartz entitled Test Instrument For Transmitters and U.S. Pat. No. 5,408,690 to Ishikawa et al. entitled Antenna Supervising Apparatus Comprising A Standing Wave Ratio Measuring Unit.